全文获取类型
收费全文 | 248篇 |
免费 | 3篇 |
专业分类
化学 | 188篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 23篇 |
物理学 | 33篇 |
出版年
2017年 | 6篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 4篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1970年 | 6篇 |
1969年 | 3篇 |
1968年 | 10篇 |
1967年 | 5篇 |
1966年 | 3篇 |
1965年 | 4篇 |
1964年 | 3篇 |
1963年 | 3篇 |
1962年 | 4篇 |
1961年 | 3篇 |
1959年 | 2篇 |
1958年 | 5篇 |
1957年 | 2篇 |
1956年 | 6篇 |
1955年 | 5篇 |
1954年 | 4篇 |
1953年 | 7篇 |
1952年 | 3篇 |
1951年 | 6篇 |
1949年 | 2篇 |
排序方式: 共有251条查询结果,搜索用时 15 毫秒
211.
212.
H.-A. Gustafsson H.H. Gutbrod B. Kolb H. Löhner B. Ludewigt A.M. Poskanzer T. Renner H. Riedesel H.G. Ritter A. Warwick H. Wieman 《Physics letters. [Part B]》1984,142(3):141-144
complete events of the symmetric collisions Ca + Ca at E/A = 400 MeV and 1050 MeV and Nb + Nb at E/A = 400 MeV and 650 MeV have been measured with the Plastic Ball/Wall 4π spectrometer. The degree of isotropy expressed by the ratio of the mean transverse to the mean longitudinal momentum in each event is determined as a function of the charged particle multiplicity. Also discussed are proton energy distributions at θcm = 90° and their multiplicity dependences. 相似文献
213.
H. A. Gustafsson H. H. Gutbrod B. Kolb H. Löhner B. Ludewigt A. M. Poskanzer T. Renner H. Riedesel H. G. Ritter T. Siemiarczuk J. Stepaniak A. Warwick H. Wieman 《Zeitschrift für Physik A Hadrons and Nuclei》1985,321(3):389-393
Evidence is presented for the strong azimuthal asymmetry between slow and fast fragments in nuclear collisions in the energy interval of 0.4 to 1 GeV per nucleon. The asymmetry gets stronger when incident energy and impact parameter decrease. The results on theA dependence of the azimuthal asymmetry are also presented. 相似文献
214.
A method is described for the spectrophotometric determination of 0-4% silicon in ferrophosphorus, following fusion with sodium peroxide in a zirconium crucible. Silicomolybdic acid is formed with sodium molybdate. The acidity is increased to 2N and the solution stood for 10 min to destroy phosphomolybdic and arsenomolybdic acids. The silicomolybdic acid is reduced with ascorbic acid and the absorbance measured at 810 nm. The colour is stable, and a standard deviation of 0.006% was achieved for 0.7% silicon. Results obtained for three samples with alternative procedures are compared. 相似文献
215.
EFFECTS OF ULTRAVIOLET RADIATION ON THE IMMUNE SYSTEM IN HUMANS 总被引:3,自引:0,他引:3
In experimental animals, exposure to UV-B radiation produces selective alterations of immune function which are mainly in the form of suppression of normal immune responses. This immune suppression is important in the development of nonmelanoma skin cancer, may influence the development and course of infectious disease and possibly protects against autoimmune reactions. The evidence that this form of immune suppression occurs in humans is less compelling and very incomplete. The wavelengths of radiation most affected by a depletion of the stratospheric ozone layer are those known to be most immunosuppressive in animals and it is likely that such depletion will increase any suppressive effect of sunlight on immunity in humans. In addition to establishing whether or not UV-B radiation can cause suppression of immune function in humans, studies are required to determine if melanin can provide protection against such suppression, the role of this suppression in the pathogenesis of skin cancer, the development of infectious disease and vaccine effectiveness, and the capacity for humans to develop adaptive, protective mechanisms which may limit damage from continued exposure to UV-B radiation. 相似文献
216.
Selenium (0.02–2 ppm), after conversion to hydrogen selenide -with sodium tetrahydroborate, can be determined by molecular emission cavity analysis. The detection limit is 7 ng of selenium. The effects of 26 ions are reported. The depressive effects of arsenic and antimony can be removed by selective volatilisation, and the enhancing effects of tellurium and sulphite by addition of tellurium to standards and by oxidation to sulphate, respectively. 相似文献
217.
Five sample presentation techniques were examined for the X-ray fluorescence spectrometric analysis of tungsten carbide alloys in powder and cemented forms. Powder samples may be oxidized by air at 600° before fusion (I), or preferably by lithium nitrate during fusion (II); the fusion is effected with lithium-lanthanum tetraborate followed by briquetting with graphite. Powder samples may also be blended with wax and briquetted (III). Cemented carbides are surface-prepared with silicon carbide before analysis (V). Briquettes prepared by blending carbide powder, lithium-lanthanum tetraborate and graphite (IV), give poor reproducibility, however, owing to micro-absorption effects the technique is not recommended. The determination of eight common elements in tungsten carbide is discussed and the relative standard deviations are 0.002–0.004 for major and 0.008–0.01 for minor elements. 相似文献
218.
R. Belcher 《Fresenius' Journal of Analytical Chemistry》1961,181(1):22-28
Summary A new technique is described which enables organic compounds to be analysed for elements and functional groups using sample weights of 30–50 micrograms (0.03 to 0.05 mg). These amounts are only just visible to the naked eye. The accuracy is similar to that of the microscale, and the technique is fairly simple.It is expected that these methods will be of value in biochemistry and associated fields where amounts of sample are often limited. The new technique is not intended to replace micro-methods. Investigations are still proceeding to develop further methods for the determination of functional groups and to refine earlier procedures. 相似文献
219.
D R Wing D J Harvey P La Droitte K Robinson S Belcher 《Journal of chromatography. A》1986,368(1):103-111
Esterified fatty acids from mouse erythrocyte and synaptosomal membranes were characterised by fused-silica capillary gas-liquid chromatography and gas chromatography-mass spectrometry. Structural information was obtained from the mass spectra of a number of derivatives including trimethylsilyl (TMS), methyl and picolinyl esters together with the TMS ethers of glycols derived from the unsaturated acids. In addition to previously characterised acids, small concentrations of several acids previously unreported from these membranes were identified. These included branched chain acids and several unsaturated acids. 相似文献
220.
L. Burnett Colin Rochester Mark Mackay Anné Proos Warwick Shaw Gabe Hegedus 《Accreditation and quality assurance》1997,2(2):76-81
The Department of Clinical Chemistry and Molecular Genetics, within the Institute of Clinical Pathology and Medical Research
at Westmead Hospital, is a medical testing laboratory operating within the public sector health system of New South Wales,
Australia. It provides acute-care pathology services to Westmead Hospital (a 900-bed tertiary referral university teaching
hospital) as well as to three district hospitals and three rural hospitals. In addition to these core clinical chemistry services,
it offers approximately 150 specialised biochemistry, pharmacology, toxicology, trace metal and molecular genetics assays
as a reference laboratory service. In 1993, the Department became Australia's first medical testing laboratory to be registered
to ISO 9001-1987/AS3901-1987. In 1995, this certification was extended to AS/NZS ISO 9001-1994. We are currently preparing
for further accreditation to ISO/IEC Guide 25-1990, with additional supplementary requirements for medical testing. This paper
describes the Quality System that the Department developed and which has been successfully maintained and extended since original
certification. Important features of the Quality System are:
1. Primary design of the Quality System to meet medical and customer needs, with subsequent addition of required ISO elements.
2. Use of national Quality Award criteria to identify key business processes.
3. Development of integrated technical non-conformance, customer complaint, staff suggestion, and quality system corrective
action procedures.
4. Implementation without external resources.
Our conclusions are that ISO 9000 Quality Systems can be applied to medical testing laboratories, and can be implemented with
minimum resource costs. Improvements in technical and service quality and business performance have resulted from this process.
However, implementation of ISO 9000 at the level of individual Departments is not ideal. Greater improvements are possible
when this process is undertaken at the level of the entire organisation.
Received: 9 September 1996 Accepted: 5 October 1996 相似文献